The present invention generally relates to apparatus for designing large electrical machines such as megawatt machines, and, more specifically, to an apparatus using a multi-phase winding.
When designing large electrical machines, such as megawatt machines, it is sometimes desirable to use a multi-phase arrangement to increase efficiency and reduce weight. For example, a 6-phase winding may consist of two 3-phase windings that have 30 electrical degree phase shift relative to each other. A significant drawback to this approach is that there is a limited number of slot number/pole number combinations that can be used. The available numbers are often widely spaced, for example; for an 8-pole electrical machine, the first available number of slots is 48, and the next is 96. If this number of available slots is incompatible with the overall design optimization, no numbers of slots can be selected in between the range 48 to 96, therefore missing a design “sweet spot”. Similar restrictions apply with other pole numbers, including 4-pole and 6-pole.
FIG. 1A through FIG. 1C show a conventional, balanced, symmetrical armature winding configuration under the prior art. FIG. 1A is diagram of the wiring arrangement for a 3-phase implementation under the prior art. The three windings beginning and ending are respectively identified as U1 to U2, W1 to W2, and V1 to V2. Slot numbers are identified from 1 to 36, for a total of 36 slots.
FIG. 1B shows a developed winding diagram for the first phase of the three phase circular windings shown in FIG. 1A if cut and laid out from end-to-end. FIG. 1C is a table laying out the winding pattern for the first phase going from U1 to U2. There are four coil groups in this phase and each coil group has three coils. There are two coil sides in each coil. The first coil has one side in slot 1 and the other in slot 8 (a span of 7); the second coil has one side in slot 2 and the other in slot 9; the third has one side in slot 3 and the other in slot 10. The second coil side of coil 1, which is in slot 8, is connected to the first coil side of coil 2, which is in slot 2; similarly the second coil side of coil 2, which is in slot 9, is connected to the first coil side of coil 3, which is in slot 3. In this fashion all these coils are connected in series to form the first clockwise positive polarity coil group. If current flows into the first coil side of coil 1 which is placed in slot 1, then the current would flow as indicated by the arrows according to the following sequence: from slot 1 to slot 8, from slot 8 to slot 2, from slot 2 to slot 9, from slot 9 to slot 3, and from slot 3 to slot 10. From slot 10, the wiring skips over to slot 19, then goes counterclockwise from slot 19 to slot 12, slot 12 to slot 18, slot 18 to slot 11, slot 11 to slot 17, and slot 17 to slot 10, completing a first counterclockwise negative polarity winding run. In this coil group, within each coil the current flows from the second coil side to the first coil side which is opposite to the first coil group. The next two coil groups repeat the pattern of first two coil groups. From slot 10, the winding skips over to slot 19 to slot 26, slot 26 to slot 20, slot 20 to slot 27, slot 27 to slot 21, and slot 21 to slot 28, completing a second clockwise positive polarity winding run. From slot 28, the winding skips to slot 1 to slot 30, slot 30 to slot 36, slot 36 to slot 29, slot 29 to slot 35, and slot 35 to slot 28, completing a second counterclockwise winding run. This completes the first phase winding. The second phase W1 start begins at slot 7 and follows a similar winding pattern with W2 ending at slot 34. The third phase V1 start begins at slot 13 and follows a similar winding pattern with V2 ending at slot 4. The second phase W1-W2 is lagging the first phase U1-U2 by 120 electrical degrees, and the third phase V1-V2 is lagging the second phase W1-W2 by 120 electrical degrees.